In a semiconductor production device or the like, a pre-aligner is mainly used in combination with a wafer handling robot and configured to grip a wafer transferred from the robot and detect a cut-out portion formed on an external periphery of the wafer called “notch” or “orientation flat,” while rotating the wafer to align the wafer to a prescribed angular orientation based on the detected information, or decide the central position of a wafer (centering).
In accordance with the recent enlargement of an external diameter of a wafer to 300 mm and the problems of wafer back surface particle contamination due to the recent miniaturization of the design rule, in a pre-aligner, it is required that a wafer gripping method be a method of gripping an edge or an end face of a wafer in place of a method of adsorbing a rear surface of a wafer.
An example of a conventional pre-aligner configured to grip an edge of a wafer is disclosed in a Patent Document 1 (Japanese Unexamined Laid-open Patent Publication No. 2003-243294) for example. This conventional wafer gripping method and wafer rotating method will be explained with reference to drawings. FIG. 9 shows a side cross-sectional view showing the aforementioned conventional pre-aligner and FIG. 10 shows a top view showing the gripping mechanism thereof.
In FIGS. 9 and 10, a grip chuck arm 120 is held by a gripping mechanism 121 comprised of two arm bodies 123 each having a generally U-shape as seen from the top with acute angle tip ends and a link for realizing linear motions of gripping portions 124 of the arm bodies 123 in radial directions toward the central axis of the apparatus main body 111 by the operation of a rotation mechanism 122 having a single driving motor 125 as a driving source. This gripping mechanism 121 is supported by a hollow rotary shaft 126 in the apparatus main body 111. The gripping mechanism 121 and the entire arm bodies 123 are configured to be rotated by a belt driving force transmitted from the driving motor 125 in a state in which the gripping portions 124 of the arm tip ends grip the wafer 101 while controlling the direction and angle with a high degree of accuracy. In other words, the gripping mechanism 121 for a wafer 101 is a link mechanism configured to simultaneously move a total of four gripping portions 124 formed on two arm bodies 123 constituting the grip chuck arm 120 in the central direction of the wafer 101 or in the direction opposite to the central direction.
Two arm bodies 123 are placed opposite to each other via the wafer 101. The arm body 123 is provided with a slider 127 which linearly guides the arm body 123 in the arrow X direction. Furthermore, the slider block 128 disposed slidably in the Y-direction perpendicular to the arrow X direction are provided with two link arms 129. The link arm 129 is configured to move the slider 127 in the arrow X direction in accordance with the linear motion of the slider block 128 in the arrow Y direction. Thus, the two arm bodies 123 can perform the gripping/releasing operation of the wafer 101.
Patent Document 1: Japanese Unexamined Laid-open Patent Publication No. 2003-243294 (see claim 5, FIGS. 1 and 2)